Thermostatic switch



Jan. l, 1946. J. A. RCDGERS THERMOSTA'IIC SWITCH Filed March 51, 1945 Patented Jan. 1, 1946 UNITED STATES PATENT -oFFIcE THERMOSTATIC SWITCH James A. Rodgers, Webster Groves, Mo., assignor to Automatic Control Corporation, St. Louis, Mo., a corporation of Delaware Application March 31, 1943, Serial No. 481,211

(Cl. 20o-137) 8 Claims.

This invention relates to improvements in thermostatic switches, and other like devices actuated by heat changes.

. An object of the invention is to Provide a safety device that is quick and positive in its action under the influence of direct heat, but which is unaiected by ambient temperature.

A further object is to provide a warping type mechanism that operates in response tok particular heat application, regardless of the starting temperature of the device.

A further object of the invention is to provide an inexpensive thermostatic switch of the warp switch type, the thermostatic elements of which have substantially the same coeliicient of expansion, and in which the operation of the switch results from the construction and association of such thermostatic elements, and their dispositions with respect to applied heat.

Additional objects of the invention will appear from the following detailed description taken in conjunction with the accompanying drawing in which:

Fig. l is a rear elevation of the device;

Fig. 2 is a side elevation;

Fig. 3 is a front elevation;

Fig. 4 is a vertical section substantially on the 1ine'44 of Fig. 1 in which the switch element is shown in open position;

- Fig. 5r is a cross section on the line 5-5 of Fig. 2;

Fig. 6 is a cross section on the line '--S of Fie. 2; and,

Fig. 7 is a fragmentary view illustrating the switch in closed position.

In the embodiment of the invention illustrated in the drawing,` the thermostatic switch is shown as a pilot operated safety switch for a gasburner. This is a valuable application, but is used as an illustration rather than as a limitation.

The switch comprises a bracket IU which is in the form of a bent plate forming an upper section II, a shoulder I2, and alower section I3. The bracket carries an electrical terminal construction having a terminal point I4 formed at the head of a bolt I5, insulated from the bracket I0, and which passes through an eye I'S of a terminal lead.

The bracket ls adapted to support the device adjacent to a pilot burner B, by an attachment through the lower section I3 thereof.

Attached to the back face of the upper section II of the bracket I0 is a member that comprises a plate I1 that is elongated beyond the upper ledge of the bracket I0. The plate I1 is provided with wings or vflanges I8 that extend forwardly above the top edge of the bracket I0. In adjusting the device in association with the pilot burner B, the ame of the pilot burner is located so that it impinges against the upper part of the plate II and between the flanges I8. The bracket I0 and the plate I1 are rigidly united at their matching faces by spot welding, or by other suitable joining means. Y

A U-shaped channel member IShas side flanges 20, connected by a channeled portion 2l. Adjacent the wings I8, the side flanges 20 and the channel portion 2| are cut away, as at 22, leaving a bridge portion 23 connecting an upper portion 24 of the member I9 with a lower portion 25 thereof. The member I9 is attached to the plate I'I by spot welding, or other suitable joining means between the plate I'I and the anges 20 on the upper section 24 and the lower section 25. That is to say, there is a united relationship between the plate II at its extreme portions with an intermediate free weakened section formed by the bridge 23.

A Contact blade 2'1 is rigidly connected at its upper extremity with the base wall of the U- shaped member I9 by spotl welding or by other suitable connecting means. The contact blade 2l is free to move within the channel member I9 throughout its length, except at its upper extremity. The contact blade carries a bracket 28 at its lower end, and an adjustable contact screw 29 is mounted in this bracket. The contact blade is electrically connected with a lead 3a through the metallic structure ofthe switch.

It will be understood that the plate Il and the U-shaped member I9 are preferably of the same metal, or of metals having substantially the same coefficient of expansion. Preferably, too, the members I'I and I9 are relatively light, so as to respond rapidly to heat changes.

From the foregoing, it will be understood that the operation of the switch is as follows:

Operation In starting position, the two members II and I9 have a starting shape and starting length. The switch is open. When heat is applied to the member I'I between the wings I8, this gives a relatively unlimited supply of heat to that portion of the member l1. It will, therefore, expand.

This restrictedly applied heat can flow to the member I9 only by conduction through the ends 24 and 25 of the member I9, and by convection and some radiation across the air gap of the channel portion 2|. These paths provide only a restricted flow of heat, and coupled with the exposure of the member I9 to ambient air, produces back of the inner member with the flanges enthe result that the member I9 expands less than gaging the same, said outer member having its does the member I1. anges and walls of the channel out away for The presence f the Cut-away DOTOII 23 has the length of said ame restricting means, and two functions. It limits the heat flow path, parproviding an upper and a lower portion, said ticularly reducing it adjacent the flame contact upper and lower portions lbeing rigidly attached area of the member II;uan`d it providesarelatively to the inner member, a switch blade having weak areaiinthe. member 49. As aresuit `ofrgthee one end iattachedfto said upperiinortiom vand exlatter, the" greater expansion of "the inner' memtending downwardly through the channel and bel n IelaVBly t0 that 0f the 0111381' member I9, below Same, a, Contact thereon, a, bracket Secured will cause bowing backward of the two members; tosaid mechanism to support the same, and a the bOWiH?,r being palfiCulaIly Concentrated; ina contactionfisaid bracket engageable by said blade the area of the bridge 23. Thedevicerwill then contact. assume the shape shown 7i; i 3.' In'ia: mechanism of the kind described, an In this position of Fig. 7, thelower portion' 25 l5; inner; and;` an ,outer elongated member having will remain substantially vertical, as it is secured substantially the same temperature coefficient of to the portion II of the member-iw;l Theemidiile expansionithaiinnermember having a front face portion of both members I1 and I9, in ,the area, with anal-ea to receive direct application of heat,

of the bridge, will bow backward. The' upperV Vthe outer member having the cross-sectional portion:V 2474A' will remain; almostestraightffbuttbye20 shape Ofia;angedtzchannel,saideouterfmember thefbowingaot-thrmiddlesportionswilt=bemovedfbeing@ disposedagainst. the,` back.` ofi; their inner: backwardly;and.v at.,an; angle;` togtne y pprtionii' member with the flanges engaging@ the-'samaeaidfi andghencegtogtheestrip I9@- 1 Y Y enten member-havingizits; flanges; and;w,ails; of

'Ihisidisplacement of;v theeportioxr-Z swillicarrye thee channel n cut; away throughout thegneat free withiitthe'upperfenff:theiswitchzbladeeZ 1I andi 25 ceivingf'areaeofsaid member; thetportionspfgsaid: thelowerlendtthereoiwill shiitxinwardligto'mkez outer membergabove: andfibelowxsaid centraigporf contact with the Contact I4. tionbeinggattachedtostherinneirnember; where- Continned f. application; off; heat: to; thea inner by; thefin-nerf-,member willexpand tofagreatenzex-i.. member. I 'I fwillznoticauseethe outertoacatchrup.-` tent# tha-ne theouter :uponvabp'li'aton otheatitx The restrictediiheat o'w :pathr betweenf-.theztwm .30 the heat IeCEVIlg area. coupled withithe .factthat airiis'rcatrsedtocircue 4f In: au. mechanism-f offth'etkind? described. a latefaboutz-.th'e member.T I 9er-to carryioiffitsf heat' pair-:efev eiongatedemembers.havingesubstantially causefit ztremainatea-:lower 'temperature than, theffsame temperatureecoefcient;of expansions, thatfof-s-therrnember.l II:` Theffairfiiowds indnced Ysaidfimembelshal/ing519.01215=llfirlsimeans byalchimneyzefiectiottnerchannei.: anditne free: 35 edlyiuniting vsaid:members:at spaced points, and.; flow of air iseincreasedby thefcutOnt portion:` holding the.b0dypOrtiOnSfOfSd mfmbelsspaed". Then result is; hat the':merriber-` Illneverfbecomesb, from? eachvother;betweenrsaidgnoints; a: switch asehot'as theffmgmber |'liduringeoperamonigffthe; blade having onebend attach-ed tothe-fupper.-por@Y bumerlBl:` Y Y Y Y f tions: ofi saidf ;membersadjaentf onen pointiof If meeuwen-stops, then-.me membersewini'io union-,iandeextendingdownwardly-between sami shortly assume equal lengths, opening the switch;- members; and below' the: Sama; and; ai device: Tmsgactione.Wmbgsenhamced byi, meeuw-that adapted to be operated by the lower end offsaid: the pilotliuel-lthenadischargeseaslahfcoolistreamel bladeont@ fme-.memb-ey,.|,1g afticjny;coolgaitu- 5. In a mechanism; ofi` thee-v kind i described, Ambient,- tempe'raturei. cMangeS-dsnote a'ectmg, means forming an integralttubular.-shapededevice the devig. Smcstheyxaciequalyyyonthptwo.. otmateriai;expansibleyand contractble inaia'cmembers, Hencey thedevie,.may..be.msbgmdi cordanceaviththeatchanges; and comprisinggtwo; as. spgm-Safety ai;fumaceuwheheitheimag.. integrally formed sides, oneiofgwhichfis adapted.; burner,Operateslintermittemly i toi; receivez direct., applicatio'nf` of-` heat changes, Whatisfclaimedis; v saidltu-bularmember beingfiformed:oimateriaifof 1;; A.; Safety... deViGef.. including. two.. @15H-gated; substantially the same coeicent of` expansion.. members of Substantially ,me..sameatemperaturei throu-ghoumzmeanszlimitingetherheat lchangessapcoefcienf; ofeggpangiom @01m-@awww.lieaingplied to one side of the tubularshaped member: sidefone. another,v meanstoy suppone the., device, against ydirecta application-.inf equal`- quantityg;v to ati-One` end; f the;.devi. extendmg,,from-.said, ibase.. 55 the f otherfsides. whereby-initreceives` more fh'eat.; end to af freeend one of,:saidmembers-:beingoab change.than'correspondingzpartsgonathe sidefopga channelsshamedfmember means atzspacedfpoints; pOSte thl'etcbl 1119.31131- Suppprfingjz the TL11QH19|-V on the open side.'oetnewhanneisshapeamember: member bvifvneesir -ad-iaenffOneizendawhelebvzf rigidlynnitingit tothe'pthenmember,saidfmemthe other4 end :will-wana uponappiisation-ofehefat fbers having'ran:insulatingfspaee betw'eenctherngr 60 thereto,. and;actuatedinieans@connectedtonthe-f whereby when heat isapplied to one in quantiotherend;toqbeiioperatedsby:thea/varnageth'ereoti. ties greater than the euqgcit'yV of the heat flow 6:Inaeheatfresponsive:device;anpairr'oilreione path, the diaerencelim expansmnlwiircause then gafedmmber's' Of Substantially.tneesameecoeffie device to -=bow and ltoe'displacethe freeeend#rela-f centfof.: expansion',iv said members zbeing disposedfi tivev` to the#-otherandbtothel supportme'ans; ande 65 alongside of; eachother: yand: rigidly@ unitn-idY Kati; meansadaptedltoebe:actuatedlby itneed-isplace'e spaced points, Stffening means on at least ones mentof-sadk-e'nd Y Y ofi-isaid fm'embersebetweeni-thea pointsotzunihn,

2. In a mechanismoftheekind'fdefscribed;a-pair-- and avweakenedpoxitionrion-'zatleast: 0I1"e a0i :said: o-'elongatedmemb'erseliaving -substantiallythe members betweenith'e points-:of-uniomiwherebyff same temperaturecoecient of expansion; thiee When=-heatiis appliedftozoneasidefof:thef-device inneri oi"-sa-id-members` having-a hat pcrt'lonwithv adjacentthe spacedpointseandV notidirectly fans wings extendingz outwardlyfromI -theMfrontl face plied to-"thei other; the' members willi expandetozff, thereoftoprovidea name restrictingmean-aine differentidegreesgfandethe stiiene'clrimeminer:willel outer-'member having#a:liangedl=channellsection; remain"substantiallywf its original shane.in:,.thne said outer member being disposed against the stiffened area, the weakened portion Hwillbend,

and one end of the device will warp relative to the other end, an actuating element engaged with said movable end, and moved for actuation thereby.

7. In a heat responsive device, a pair of elongated members of substantially the same coeilicient of expansion, said members being disposed alongside of each other and rigidly united at spaced points, stiifening means on one of said members between the points of union, said other member having a portion weakened against bending, also between the points of union, Whereby when heat is applied directly to the stiiened one of said members and not to the other, the one will expand more than the other, and the weakened one will iex principally in the weakened portion and one united point will warp relative to the other, an actuating element attached to the flexing end and rocked thereby to produce an actuating movement.

8. In a device of the kind described for use ln detecting flame conditions at a. given point,

comprising an inner member adapted to be disposed adjacent the name and having a front face against which the name can impinge, a pair of wing members on opposite sides of the front face extending therefrom toward the flame to concentrate the ilame upon the front face, an outer member of substantially the same coeiiicient of expansion as the inner member, and spaced from the flame and insulated from the inner member, means rigidly attaching said members together at spa/ced points, said attaching means constituting restricted heat-conducting paths from one member to the other, means to support the device, an actuating element attached to the device adjacent one end opposite the supporting means, said inner memberl when flame is impinged upon the front face, expanding more rapidly than the outer member, and the device warping about the supporting means 20 to displace the actuating element.

JAMES A. RoDGERs. 

